This invention relates generally to orthodontic wire and more specifically it relates to a multi-coated orthodontic wire and a method for making such orthodontic wire.
The coating of metallic orthodontic wire with a layer of non-metallic material is known. Examples are shown in the prior art, namely U.S. Pat. No. 4,585,414, as well as in Applicant's own U.S. Pat. No. 4,731,018.
One of the reasons for coating an orthodontic wire, especially an orthodontic arch wire, is to impart to the wire a color that will blend with teeth of the arch when the arch wire is in use. In this way the arch wire is made relatively inconspicuous, a desirable attribute for appearance.
The present invention relates to an orthodontic wire which is constructed in a new and unique way to present an appearance corresponding to that of tooth color so that as an arch wire, it will be rendered relatively inconspicuous.
Prior coated orthodontic wires contain coloration in the coating material that matches the tooth color. If this material is worn away, the bare metal becomes exposed.
The present invention is directed to a new and unique construction for an orthodontic wire which will provide improved quality for the maintenance of tooth coloration. According to a preferred embodiment of the present invention, a very thin layer of tooth color material is applied to the metal wire. This thin layer of tooth color material is then covered by an overlying clear protective layer. In this way the tooth color material can be selected for its desired coloration, and ease of its attachment or bonding to metal wire, without major concern for its inherent resistance to wear. Wear resistance and durability are imparted by the clear overlying protective layer with the result that the dual attributes of desired tooth color appearance and durable exterior are achieved in an orthodontic wire that is predominantly metallic.
Related aspects of the invention involve various methods by which the described orthodontic wire is fabricated. Where a metal wire of circular cross section is to be coated by passing the wire through a processing line that applies the coatings, it is been found important to keep the wire from twisting; according to a further aspect of the invention, a lip, or protuberance, is provided at a given location on the circumference of the wire to act as a locator for accurately circumferentially locating the wire with respect to the process line as it passes through. After the coating operations have been completed, this protuberance and the portions of the coatings which overlie it are removed, thereby leaving a partially coated arch wire. The partial coating extends around a majority of the circumference of the wire so that exposed metal is along a limited circumferential region. This type of wire is especially useful in the practice of applicant's invention as described in U.S. Pat. No. 4,731,018 where a limited circumferential region of the arch wire is intentionally left as bare metal to provide a better joint with an orthodontic bracket that receives the arch wire. Although the present invention is especially useful for fabricating orthodontic wire to be used as orthodontic arch wire, the dual coated orthodontic wire of the present invention may be used for fabricating other wire type orthodontic devices, such as a ball clasp for example.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.